Machine-switching telephone-exchange system



NM2, 33 y 1R. STOKELY MACHINE swITcHNG TELEPHONE EXCHANGE SYSTEM Filedme@ s snetsgsheei 5 Nm., E3 9 i923 EAM-,mg R. @Tamm l MACHINE SWITCHINGTELEPHONE EXCHANGE SYSTEM Filed Dec. 8 1925 5 Sheets-5h96?, 4

No 'm ma l-Qmmg R. STOKELY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEMFiled Dec. 8 1920 5 Sheets-Sheet 5 BAY BTOXELY, F FLORAL PARK, NEW YORK,ASSIGNGB T@ WESTIBH- 1 COIPANY, INCORPORATED, 0l' NEW YORK, N. Y., .AGQBPQBATEON @E Le HACmSWITCHING TELEPHONE-BGE @Y i M Application liedDecember l, im. Berta! lo. MAN.

To all whom z't may conm:

Be it known that I, RAY S'mxnnr, a citizen of the United States,residing at Floral Park, in the county of Nassau, State of New I York,have invented certain new and useful IImprovements in Machine-*SwitchiTelehone-Exchange Systems, of which t e fol,-

owing is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems employing machineswitching and its object is to provide an improved circuit arrangementto take care of toll calls to and from full automatic offices.

This invention is an improvement in the s stem shown anddescribed in m Aapplication filed July 26, 1919, Serial o. 313,521 for telephoneexchange system.

In that application a circuit arrangement is disclosed whereby thecalling supervisory lamp at the toll operators position is flashed at acertain rate if any selector encounters ay busy trunk group in theprocess of building up a connection and at another rate if the connectorfinds the called line busy.

` -In the system disclosed in the above-identified application, however,the lamp will give the busy line flashing si nal to the toll operatornot only if the ca led line is ac- :m tually busy, but also if such lineis out of order, or 1f for an reason,except encountering a busy trungroup building up the connection does not` proceed to the oint where theconnector tests the line and) finds it to be idle. Thus, the operatormay be given an erroneous signal. p e present invention provides animproved circuit arrangement whereby the busy line flashing signal ofthe calling supervisory lamp in the c'ord circuit at the toll operatorsposition is only iven when the lclonnector finds the selecte lineactually usy.

The invention will be more readily under- 46 stood from a detaileddescription of the operation of the system.

Referring to the drawings, Fig. 1 shows a toll cord circuit, Fig. 2shows a trunk circuit outgoing from the toll board to a full 0mechanical or automatic office, Fig. 3 shows a selector circuit at thefull mechanical oflice; Fig. 4 shows a toll transmission selectorrepeater, and Fig. 5 shows a combination toll and local connector.Referring first to Fig. 1, this drawing the process of L tollsupervisory lamp shows a cord circuit at the toll operator@ position.The left hand side of this circuit will be called the toll end and theright hand side will be called the `tell and4 trupk and. The operatoranswers an incoming call by inserting the 113g T of the toll end in theanswering jac in the ordinary manner. If the called subscriber islocated in a nearf by exchange, the call is completed by irt.- ing theplug TT of the trunk and' toll end` in a toll switching trunk jack TSJ.operator then actuates the dialing and monitoring key DK which causesthe relay B--S to operate, which in operating energizes a monitoringrelay (not shown) place the perators telephone set in a. monitoringpesition on the cord. The operatori-"now tu the dial D for the firstdigit of the Wanted a number. The dial in movin out of its nor# malposition short circuits t e relay B-3t 35 permitting the relay E-7 2 tooperate. lR.e' lay E72 in operatin locks itselfto batter f and transfersthe tip of the plu 'u x through the impulse springs ofA the l to thebattery. The dial, in returnin to nor. mal, interrupts the battery tothe tip of the plug causin the impulse relay of the trunk circuit of ig.2 to operate intermittently, theV number of times dependin upon thedigit involved. This impulse re ay, in thus operating. causes thesetting of the selector circuit of Fig. 3, which thereupon automaticallypicks out an idle trunk. in the selected level. When the operator has'operated the dial for all the digits involved which causes the lastswitch to be set on the desired line she restores the monitoring key DK.M the called line is not busy, the trunk and lights as a ringing vsignal, whereupon t e operator by deprcss- @5 ing ringing key RK causesthe connect/0 to start the ringing of the called linewhic rinlgingcontinues automatically. unti'l the cal ed party answers, whereupon thecurrent is out oi and the lamp-:.100 is ex mi@ tinguished. When thecalled subscriber re; places his receiver, this lamp again liglitafaa adisconnect signal.

If the called line is busy or if one of thai! selectors had failed tofind an idle trunk, the, W5 lamp 100 will flash, the frequency oftheflashes depending upon the busy condition encountered. The tolloperator in response to the dashing of the lain removes the plu TT ofthe t 1. and to end of the cor BHO from the toll switching jack TSJ, butbefore removing the toll plug T from jack J, the operator by means ofher ringing key RK,- rmgs on the toll line terminating at the ]ack J tonotify the distant operator that the line is clear. lf the distantoperator rings first, however, the toll supervisory lamp 101 lights andwhen the operator actuates listening key LK, or pulls out the plug T,this lamp 1s extinguished.

If the called subscriber is a distant one reached over a toll line, thetoll operator inserts the plug TT of the trunk and toll end in theproper jack similar to jack J and by means of her ringing key R Kapplies alternating current to such toll line to signal the distantoperator. When the operator at the distant end of the toll line appliesringing current to the trunk at the termination of the conversation thetoll supervisor lamp 101 lights until the listening ke L is operated orthe connection is ta en own. The keys K and K serve, when operated, todisconnect either end of the cord from the operators telephone set whenthe operator is talkin on the other end. When the plug T of t e toll endis inserted in toll answering jack J, relay itl-156 operates, in turnoperating relay B-162. Relay B-162 opens the circult of relay E-162preventing the toll supervisory lamp 101 from lightin When the plugP TTof the trunk and tol end is inserted in toll switching trunk jackTSJ,'relay E-99 operates in series with relay E-155 and the lowerwinding of relay E-156. Relay E-99 disconnects the busy test equipmentof the operators telephone set from the tip of the cord and connects thetip of the cord through to the ringing key. Relay E--l is marginal anddoes not operate at this time on account of the high resistance in thesleeve of the trunk circuit.

Ringing current applied by a distant operator operates the rela A--196which releases rela B162. he latter relay in releasing liglits the tollsupervisory lamp 101 and operates rela lil-162 in parallel with thelamp. Relay dl-162 locks u under the control of the llstening key L andrelay E--156 so that the lamp remains lighted after the ringing ceasesand the relay B-162 is re-operated through the back Contact of relayA--196. The lamp 101 may be extinguished by operating the listening keywhich releases relay E--lti or by' taking down the connection whichreleases relays E-156 and E-162- Relay lil- 162 is made slow inoperating to guard against the possibility of lam 101 being lighted byMorse impulses. Re ay A-196 may be operated for a short time by Morseimpulses but will not remain operated long enough to cause the 0 rationof rela lil- 162. In case relay +162 should re ease momentarily, the

Slow operatin feature of the relay E-162 will give the ormer time tore-operate before the relay E--162 operates and locks. When both ends ofthe cord are inserted in toll line jacks the marginal relay E-155disconnects the rela B-43 from the cord circuit. If, on a tiirough tollconnection, the splitting key K is operated to disconnect the trunk andtoll end from the operators telephone set, relay B-43 is bridged acrossthe trunk and toil end so that it will operate when ringing current isreceived from the distant operators position connected with the calledtoll line, the trunk and toll end and flash the lamp 100. When thesplittin the circuit or relay B-43 is opened.

Referringlnow to Fig. 2 which represents a toll switc ing trunk overwhich a connection is extended to a nearby exchange, relay 0 2 operatesover its right hand wlnding when t e operator inserts the plug TT intojack TSJ and by attracting its armature closes a looo circuit leading tothe impulse relay A-3, Fig. 3, of the first selector at such excha whichin operating energizes slow rela -3 to prepare the im ulse circuit. W enthe dialing key DK 1s thrown and the dial is operated, relay A-2 orates, connecting relay I--2 across the 00p leadin to the impulse relayA-3, 3. Relay -2 in operating causes rela -2 to o erate, which relayshunts the le t hand win ing of relay C-2 whereupon the latter relayreleases, the circuit through its ri ht hand winding being opened whenre ay E-72, Fig. 1, operates as the dial is moved out of its normalposition. Relay D-2 in operating operates relay E-Q which locks up tothe ground at the inner left contact of relay 13 2, now energized. RelayE--2 at its outer left contact locks up relay D-2, independently of itsoriginal energizing circuit Which lead over the front contact of relaI2. The dial in restorin intermittent y operates relays A-Q and 2, relayA-Q intermittently openin the loo circuit to the relay A-B to set ielirst se ector and relay 1 2 alternately openin and closing a shunt patharound relay 2. If, during the operation of building up a connection,one of the selectors fails to find an idle trunk in the selected group,it opens the loop circuit including relays A--3 and I-2. Relay I--Q inclosing its back contact permanently shunts out relay D-2. Relay D-2 inclosing its right hand back contact operates relay H2. Relay H-Q locks11p and connects interrupted battery of 60 impulses per minute to thewinding of relay C-2 in shunt of the resistance 200. Relay B-43 in thecord (Fig. 1) follows these impulses and ashes the supervisory lamplOOto indicate to the operator the failure to find an idle trunk.

key K is in its normal position lll) arm ature 204,

ramena In case the called line is busy, the polarized rela F-2 operatesas in the case ,of a successful call but. in this case a. differentinterrupter is connected in circuit .to flash the lamp 100 at adifferent rate to mdxcate to the o rator thebusy condition of theselected e.

In case the called subscribers line is found to be idle by the connector(Fig. 5) this condition causes the polarized relay7 F 2 to operate andcause lam 100 to ight as a r1 ing si al when el operator restores the eyD Relay 'F 2 1n operating also energizes relay G 2 which cuts the trunkthrou h, thus disconnecting the relays C .2 and *5 2 from the circuitleading back to the toll operators tion.

Having describe in a general manner the operation of the system, a callwill-now be traced in detail.

The toll operator, having been informed of the number of the wanted lineand assuming this line to be in a nearby exchange,

tests for an idle trunk by touching the tip of her lug TT to the sleeveof the jack TSJ of tllie toll switching trunk in the well known manner,and if she does not receive a click in her receiver she inserts therplug TT into the toll switching trunk jack SJ. The following circuit isthereupon 'closed to operate relays E 99, (Fig. 1) and B 2 'g. 2) freepole of battery, relays E 99, E 155, lowei` Winding of relay E 156,sleeves of the plu kand jack, relay B 2 to ground. Relays 155 and E 156do not operate in the circuit.

Relay E 99 in operating disconnects the operators busy test circuit fromthe tip of the cord. Relay B 2 (Fig. 2 in operating prepares certaincircuits w ich will be traced later. This trunk will now test busy atthe other operators positions due ,to battery ap lied to the sleevemultiples by the sleeve o? the plug TT. The insertion of the plug alsocloses .the following circuit to en ergize relay C 2: free (pole ofbattery, resistance 200, right han winding of relay C 2, conductor 201,armature 202 of relay G 2, conductor 203, ring of the jack TSJ, ring ofthe plug TT, conductor 120, lower normal contact of ringing key RK,right hand winding of retardation coil 121, relay B 43 armature and backcontact of relay l3l55 which is not operated when the plug TT isinserted in the toll trunk switching jack, but only when it is in`serted in a toll line leading to a distant office, left hand winding ofretardation coil 121 upper normal contact of ringing key R', armatureand front contact of relay E-99, conductor 102, right hand normalcontact of relay E 72, conductor 103, tip of the plu TT, tip of the jackTSJ,

' ack contact of relay G 2, and relay A 2 to ground. Relay A 2 ismarginal and does not operate in this circuit. Relay C 2 in attractingits armature closes the following circuitto 'operate relay A 3, Fig. 3,which is the impulserelay of the first selector, shown in Fig. 3; A'freepole of battery, lower winding of relay A B (Fig. 3), conductor 300,back contact'and armature 301 of relay D 3, conductor 302,

conductor 205, conductor 206, outer left4 hand armature and back contactof relay H 2, conductor 207, armature and front contact of relay C 2,left hand winding of relay @-2, conductors 299 and 209. inner rightarmature and front contact of relay B 2, conductor 210, polarized relayF 2, conductor 211, conductor 212, conductor 303, armature 304 and backcontact of relay D 3, conductor 305, upper winding of relay A 3,conductor 306, normally closed contact of switch 307, operated on theeleventh rotary step of the selector, to ground. The operator now throwsthe dialing and monitoring key DK, the listening key LK which wasoperated in order to connect the operators set with the calling linehaving been restored, whereupon a circuit is closed tracting itsarmature closes a circuit to conneet the operators head set across thecord for monitoringpurposes. She now rotates the dial D for the firstdigit of the wanted number. The closure ofthe contact 1011 of the dialas the dial moves oil' normal shunts the rela B 34, which permits themarginal relay 72 to operate and releases relay B 34. Relay E 72 inattracting its left hand armature locks itself to ground at a contact ofthe dialing key DK which when actuated remains in its operated positionuntil manually released by the operator. Relay E 72 in closing its righthand contact opens the bridge containing relay B 43 and connects freepole of battery through the impulse Contact 108 of the dial to the 'tipof the plug. The opening of the said bridge opens the circuit heretoforetraced through the right hand winding of relay (1 2. Marginal relay A 2now operates in series with the impulse Contact of the dial, the circuitbeing as follows: free pole of battery, resistance 109, impulse contact108, right hand' armature and front contact of relay E 72, conductor103, tip of the plug TT, tip of the jack TSJ, armature 204 and backcontact of relay G 2, conductor 213 and relay A 2 to ground. Relay A 2in attracting its left hand armature bridges relay I 2 across the tipand ring of the cord in parallel with the left hand winding of relay C2. Relay 1 2 in attracting its armature closes a circuit to operaterelay D 2 as follows: free pole ot battery, resistance 215, relay D 2,conductor 216, right armature and front contact ot relay 1 2, conductor217, contact 218 of all G2 to ground. Relay D--2 in attracting its leftarmature short circuits the left hand winding of relay C-2 whichthereupon releases, thus opening one of the bridges to the impulse relayA-3 and leaving bridged across the circuit only relay I-2. This circuitmay be traced as follows: free pole of battery, lower winding of relayA--3, conductor 300, armature 301 and back Contact of relay D-3,conductorA 302, conductors 205 and 206, outer left hand armature andback contact of relay lI--2, conductor 207, conductor 208, relay I2,left hand armature and front contact of relay A-2, conductor 211,conductor 212, conductor 303, armature 304 and back contact of relayD-3, conductor 305, upper winding of relay A-3 and upper normal contactsof switch 307 to ground. Relay D2 at its right armature and frontcontact closes the followin circuit to operate relay E2: free pole ofattery, relay E-2, conductor 220, right armature and front contact ofrelay D--2, conductor 221, conductors 222 and 228, inner left armatureand front contact of relay B2 to ground. Relay E-2 in attracting itsinner right armature locks itself to grounded conductor 222. The funetion of this relay will be later described. Dial D, Fig. 1, in returningto normal, interrupts at. its impulse contact 108 the circuit of theimpulse relay A-2, Fig. 2, which at its left armature interrupts thecircuit of the impulse relay A-3, Fig. 3, the number of timescorresponding to the first digit of the wanted number. Upon eachretraction of the armature of relay A-3, the following circuit is closedfor the vertical magnet 310 of the first selector: grounded armature311, and back contact ofrelay D3, conductor 312, armature and backcontact of relay A-B, lower armature and front contact of relay B-3,slow relay C-3, ver-- tical magnet 310, and free pole of battery On thefirst step of the selector off normal springs 313 close the followingcircuit for relay 314: free pole of battery, relay 314, conductor 315,ofi1 normal springs 313, conductors 316, 317, armature and front contactof relay C--3 to ground at the armature and front contact of relaynB-3.Relay 314 in attractin its upper -'armature locks itself over thefollowing circuit: free pole of battery, relay 314, conductor 315, oil'normal contact 313, conductor 316, armature andvback contact of rotarymagnet 318, conductor 319, conductor 320, upper armature andlffrontcontact of relay 314, conductor 3211Y toground at the armature 311 andback contactofgrelay D-3. Upon the cessation of "thefirnpulses, relayA-3 remains energized and consequently relay C-3 which is slow torelease, after an interval releases, whereupon the following circuit isclosed to energize the rotary magnet 318 of the serelay lector to stepthe selector brushes on to the first trunk in the selected level: freepole of battery, magnet 318, conductor 322, lower armature and frontContact of relay 314, upper normal contact of relay C3, upper armatureand front contact of relay B-3 to ground. At the end of its stroke, therotary magnet 318 opens the locking circuit traced for relay 314. Relay314 in retracting its lower armature opens the circuit of the rotarymagnet. If the first trunk is busy, ground is )resent on the testmultiple 323 thereof, whereby the following circuit is closed toenergize relay 314: grounded muitiple 323, test brush 324, conductor325, armature 326 and back contact of. relay D-3, conductors 327, 319,back contact ano armature of magnet 318, conductor 316, contact 313,conductor 315, relay 314 to free pole of battery. Relay 314 inattracting its upper armature again locks itself through the backcontact of the rotary magnet and in attracting its lower armature againcloses the circuit of the rotary magnet whereupon the selector brushesare lstepped to the next trunk. This interaction of the rela 314 androtary magnet is continued unti an idle trunk is found which isindicated by the absence of round on the test multiple 323 thereof. henthe rotary magnet at the end of its stroke. potions the brushes on tothis idle trunk no ground being present, relay 314 does not energize butswitching relay D-3 energizes over the following circuit: free pole ofbattery, rela 314, conductor 315, contact 313, con uctor 316, armatureand back contact of rotary magnet 318, conductor 319, conductor 327,conductor 328, relay D-3, conductor 329, lower normal contact of switch307, conduc-v tor 330, to ground at the upper armature and front contactof relay B-3. Relay 314 is marginal and does not operate in thiscircuit. D-3 in attracting its armatures 304 and 301 extends the talkingconductors through to the selector brushes and cuts oi impulse relay A3.

Assuming now that the selector has failed to find an i-dle trunk. Inthat event on the eleventh rotary step, switch 307 is operated by theshaft of the selector and opens the circuit of the impulse relay 'A-3which causes the selector (Fig. 3) to restore. The opening of the loopcircuit also causes relay I-2 (Fig. 2) to be permanently deenergized.When the operator transmits all the digits, relay A-2 in remainingattracted and the' relay I--2 being inert, the following short circuitis closed about the slow relay D-2 to cause the same to release: freepole of battery, resistance 215, right hand armature an front contact ofrelay A--2, armature and back contact of relay 1 2, conductor 217,contact 218, to ground. It will be understood that relay D-2 is slow torelease as shown and holds up during the impulses. Relay D 2 inretracting its right armature operates relay H-2 over the followingcircuit: free pole of battery, relay H2, conductor 290, right armatureand back contact of relay DV-2, conductor 220, inner right hand armatureand front contact of relay E-2 to ground on conductor 222. Relay H-2 inattracting its inner left armature locks itself up to grounded conductor222 and in attracting its inner right armature connects interrupter 223to the inner left hand armature and front co'n tact of relay E-2 toshunt the resistance 200 t'o cause supervisory relay B-43 in the cordcircuit to flash the trunk and toll supervisory lamp at the rate of 60flashes per minute when the operator restores the key DK which she doesafter transmitting all the sets of impulses. This rate of flashing willindicate to the operator that one of the switches has encountered a busytrunk group whereupon she will pull out the plug and will then wait andset up the connection later. Although the interrupting machine 223 isconnected to the front contact of relay E-2 as soon as relay D--2releases and relay H-2 operates this is not effective to flash the lampuntil the operator, after having turned the dial for the last time,releases her dialing key DK, Fig. 1. The opening of the lowermostcontact of this key releases relay E-72 which in retracting its rightarmature again closes the loop circuit includin the right hand windingof relay (1 2, 2, and the relay A 2, Fi 2 and B-'43 (Fig. 1). It will,of course, a understood if no idle trunk is found relay D-3 is notenergized. attracting its outer left armature interposes a break 1n theloop circuit leading to the selector (Fig. 3) thus preventing thesubsequent impulses from selector circuit.

Assuming, however, that an idle trunk was found, the seizure of the tolltransmis` sion selector repeater Fig. 4, in which such trunk terminates,causes the closure of the following circuit for impulse relay A-4thereat, Fig. 4: free pole of battery, left hand winding of relay A-4,conductor 400, contact 401 of relay B-4, conductor 402, contact 403 ofrelay F-4, conductor 409, lower left hand winding of repeating coil 404,conductor 408, multiple terminal 334, brush 333, conductor 332, armature301 and front contact of relay D-3, conductors 302, 205, 206, leftarmature and back contact of relay H-2, conductors 207, 208, relay I,-2,left hand armature and front contact of relay A--2, conductor 211, 212,303, armature 304 and front contact of relay D-3, conductor 352, brush350, multiple terminal 351, conductor 407, upper left hand winding ofrepeating coil 404, conductor 405, contact relay inV attracting itsouter The relay H-2 inl passing to the l 406 of relay F-4, conductor.410, contact 411 of relay B--4, conductor 412-, through; the rightwinding of relay A-4 to groundV at the lower normal, contact of theswitch' 413 which is only operated on the eleventh 70 rotary step of theselector re ater. The impulse relay A-4 in attracting its ri ht.armature energizes slow rela 414. is

left armature closes a circuit for relay 336 which in. `at-l tractingits armature supplies a local ground to-the test multi le 323 to causethis.: l trunk to test busy. Vhen the. relay 414 operates it closes atits right hand armature the following circuit for relay D-4: groundright armature and `front contact of relay 414, conductors 415 and 416,contact 417 of relay (lr-4, conductor 418, outer. right hand armatureand back contact of. relay F-4. conductor 419, relay D-4 tol free poleof battery.

The second operation of the dial by the operator transmits thecorresponding digit of the called line causing relay A-2, F1g.- 2, toopen and close the loop circuit for the relay A-4, which in vibratingits right hand armature transmits impulses over the following circuit tothe vertical magnet 420 ofthe selector repeater: ground, right armatureand back contact of relay A 4, inner left armature and front contact ofrelayV 414, conductor 421, armature 422 and back. contact of relay (3i-4, conductor 423, slow relay 424, magnet 420 to free pole of battery.The brushes of the selector are thus elevated to the desired level. Whenthe dial returns to normal and maintains the relay A-2 (Fig. 2)energized, relay A-4 remains energized and, after a slight interval,slow relay 424 releases. When the relay 424 operated on the firstimpulse. and the selector took its first step, relay 425 correspondingto relay 314 (Fig. 3).. operated over the following circuit: free poleof battery, relay 425, upper contact of off normal switch 426, conductor427, armature and front contact of relay 424, conductor 432, armature429 and back contact of relay 430 to ground. In attracting its innerarmature, relay 425 locks itself to its inner armature, this circuitincludico ing the armature and back contact of rotaryv magnet 431. Thesecircuits are similar to those of the selector of Fig. 3. U on thecessation of the impulses and the re ease of 12 the slow relay 424, thecircuit of the rotary magnet is closed as follows: free pole of battery,magnet 431, outer armature and front contact of relay 425, normaloontact of relay 424, conductor 432, to ground at the armature 429 ofslow relay 430. The rotary magnet advances the brushes on to theterminals of the first trunk and at the end of its stroke opens thelocking circuit of the relay 42,5 which releases opeg the 330 circuit ofthe rotary magnet. If the trunk is busy, relay 425 again energizes overthe following circuit: free pole of battery, relay 425, upper contact ofswitch 426, conductor 427, armature and back contact of rotary magnet431, conductor 433, back contact and armature 434 of relay G4,concircuit of relay 425 which in retracting its armature opens thecircuit of the rotary magnet-431. The switch 413 corresponds to theswitch 307 of the selector circuit, Fig. 3. Its function is to open thecircuit of the impulse relay A-4 on the eleventh rota stop of theselector, that is to say, if al the trunks in the group are busy. Theopening of this circuit releases the switch and causes relay 1 2, Fig.2, to become permanently inert which causes the release of slow relayD-2 and prepares a circuit for the interrupter 223 which results in theflashing of the trunk and toll supervisor lamp 100 when the operatorrestores her ialing ke as described in detail in connection withv Fig.3. If, however, an idle trunk is found, relay G-4, which corresponds torelay D--3, Fig. 3, operates over the following circuit: free pole ofbattery, relay 425, upper contact of switch 426, conductor 427, amatureand back contact of magnet 431, conductor 433, relay G4, conductor 440,upper contact of switch 413, conductors 441, 415, toground at the rightamature and front contact of relay 414. Relay 425 is marginal and doesnot operate in .this circuit in series with the relay G-4. Relay G-4operates and in attracting its armatures 442 and 443 extends thetalkingconductors through to the talking brushes444 and 445. Theattraction of the armature 434 of relay G-4 grounds the test brush 438and cons uently test multiple 439 of the selected trun causing the sameto test busy to other selectors. The contact 446 is made before thecontact 417 is broken b the armature 447 of the relay G-4.

onsequently relay D4 is maintained energized over the following circuit:free pole of battery, relay D-4, conductor 419,

4'outer right armature and back contact ofrelay F--4, conductor 418,contact 446. armature 447, conductor 448, brush 449, multiple 450,control conductor 451, conductor 500 (Fig. 5), conductor 501, armature502 and back contact of relay K--5, conductor 503, sleeve conductor 550,conductor 452, multiple 439, brush 438, conductor 437, armature and backcontact 436 of relay1430, conductor 435, armature 434 and front contactof relay G-4, conductor 415,to `ground at the right armature andfrontcontact of slow relay 414. Thus,

ing up their own connections. The seizure of the connector causes theclosing of the following circuit for the impulse relay A-5z free p'oleof battery, upper winding of relay A-5, conductor 504, contact 575 ofrela D'-5. conductor 505, left winding of s ow relay J-5, conductor 507,lowermost armature and back contact of relay K-5, ring conductor 546,conductor 453, multiple 454, brush 445, conductor 455, armature 443 andfront contact of relay G4, left armature and front contact of relay A-4,ring conductor 457, armature 456 and back contact of rela H--4,conductor 458, lower right han winding of the repeating coil 404,resistance 459, conductor 460, inner left armature and front contact ofrelay D-4, left winding of relay 461, conductors 462, 463, resistance464, upper right hand winding of repeating coil 404, conductor 465,upper armature and back contact of relay H-4, conductor 466, uppermostarmature and front contact of relay G-4. brush 444, multiple 467, tipconductor 510, upper armature and back Contact lof relay K--5, conductor576, back Contact 577 of relay D-5, lower winding of relay A-5 toground. When relay G-4 operates a circuit is also closed through the'right hand winding .of relay 461 which leads over 476, 477, 470,armature 434 and front contact of (ir-f4, conductor 415, to ground atthe armature and front contact of relay 414. The current in the circuitjust traced is opposite in direction to that in the left hand winding ofthis relay. Consequently this relay does not operate at this time.Relays J5 and A-5 operate in the circuit previously traced therefor, theformer at its innermost right armature closing a locking circuit foritself as follows: free pole of battery, right-winding and rightlnnermost armature and front contact of J--5, conductor 531, conductor515, to ground at the armature 516, and front contact of slow relay B--5which is energized upon the energization of the impulse relay A-5. RelayB-5 unds the sleeve wire 517, leading ,to t e test multiples in thelocal selectors, this circuit leading from grounded armature 516,conductor 515, to conductor 517- The return of the dial to normal intransmitting the tens digitiof the wanted number interrupts the circuitof relay A-2, Fig. l2 which in turn interrupts the circuit of theimpulse relay A-4, Fig. 4 which in vibrating its armatures causes theimpulse relay A-5 of the connector to transmit impulses to the verticalmagnet 518 of the connector. vThe circuit for the first impulse is asfollows: free pole of battery, magnet 518, slow relay 519, right contact.of olf normal switch 520 conductor 521., lower armature and frontcontact of relay B-5 to ground at the armature and back contact of theimpulse relay A-5. At the first step of the connector, the off normal srings 520 are shifted and the succeeding impulses are transmitted by wayof the upper armature and front contact of relay 519 and the contact 522now closed of the off normal springs 520. Relay F5 is operated by itslower Windin when relay 519 operates, this circuit inc uding theinnermost right armature of relay J- and grounded armature 516 of relayB--5. Relay F5 locks up to the control lead 500. The connector brushesare thus lifted to the desired level and upon the cessation of theimpulses, im ulse relay A5 remains energized and re ay 519 in serieswith the 'vertical magnet releases preparing the circuit of the rotarymagnet 523. The units impulses pass through the back contact of theimpulse relay A-5, lower armature and front contact of relay l3-5,conductor 521, oi normal contact 522 back contact of slow relay 519,conductor 524, innermost left armature and back contact of relay (ir-5,conductor 525, uppermost armature and back contact of relay H-, rbtarymagnet 523 to free pole of battery. The connector is thus stepped aroundinto engagement with the desired If this line is idle, full potential ispresent on its test multiple 526 through the cut off winding of the lineswitch, and the following circuit is closed to operate relay H5:multiple 526, brush 527, conductor 528, armature 540 and back Contact ofrelay E-5, conductor 529, upper winding of relay H-5, conductor 530,right hand armature and back contact of relay G-5, conductor 531,conductor 515, armature 516 of relay B-5 to ground. Relay H-5 inattracting its armature 532 locks itself to the e grounded sleeve wire550 and extends this grounded conductor over conductor 533, middle rightarmature and front contact of relay J5, conductor 534 t0 the relay K-5.Relay K-5 in attracting its armature 502 disconnects the grounded sleevewire 550 from the control lead 500 leading back to the. relay D-4, Fig.4 of the selector repeater. Relay D-4 in retracting its outer left handarmature operates relay F-4, to reverse the' current flow in the circuitleading back to the operators cord to light the lamp as a 'ringingsignal, Fig. 4, over the following circuit: free pole of battery, relayF-4, conductor 469, outer left armature and back Contact of relay D-4,conductor 470, armature 434 and front contact of relay (3i-'4, conductor415 to ground at the right armature and front contact of relay 414.llelay F-4 in attracting its outer right armature applies the followingsubstitute ground to hold up the relay F--5 to prevent ringin fromoccurring at this time: ground. le t hand armature and back contact ofrelay 471, conductor 472, outer left armature and back contact of relayB-4outer ri ht armature and front contact of relay -4, control conductor418, contactv446 and armature 447 of relay G--4, conductor 448, brush449, multiple 450, conductor 451, conductor 500, front Contact andarmature 535 and lower winding of rela F-5 to free pole of battery. Theoperatlon of relay K- by releasing D-4 and operating relay F-4 whichcaused the reversal of direction of the current flow in the loop leadingback to the toll operators position opens the locking circuit relay F-5'and unless a substitute circuit is provided .for holding up relay F-5`after rela K-5 operates the ringingv operation wo d' automatically takeplace. This is prevented by applying round to the control conductor 500over t e circuit traced to hold the relay F- until the operator, bydepressing a key as will be explained, releases relay F-5 to start theautomatic ringing operation. The release of the relay D-4 and theconsequent energizat'ion of relay F-4 as described reverses thedirection of current flow in the talking conductors leading back to theoperators position. After the operator has turned the dial for the lasttime, shev restores her dialing key DK which releases relay E 72 whichdisconnects the vdial from the tip of the plug causing the release ofthe relay A--2, Fig. 2, and causes the closure of an energizing circuitfor the right hand winding of relay Cf-2, relay B-43 and relay A 2.Relay A-2, it will be remembered, releases under this condition and inretracting its left armature deenergizes relay I-2, which in releasingcauses the release of relay D-2. The polarized relay -1-2 is now bridgedacross the following circuit: upper talking conductor 212, Fig. v2,conductor 211, polarized relay F -2, conductor 210, inner right armatureand front contact of relay B2, conductor 209, conductor 299, left handwinding of relay C-2, armature and front contact of relay C-2, conductor207, outer left armature and back contact of relay H-2, conductor 206 tolower talking conductor 205. The reversal of the directlon of currentvin these talking sgi conductors due to the operation of Irelay 1"-4causes the rela F-2 to operate closing the following c1rcuit for relayG-2: free pole of battery, relay G-2, conductor 224, contact 225 ofrelay F-2, conductors 226, 227, 228, inner left armature and frontcontact of relay B-2 to ground. Relay G-2 locks itself up over thefollowing circuit: free pole of battery, relay G-2, conductors 224, 229,front contact and armature 230 of relay G-2, conductor 231, conductors227, 228 to ground at the inner left hand armature of relay B-2. RelayG--2.

connects the talking conductors of Fig: 2 through to the talkingconductors of ig. 1 whereupon the trunk and toll relay B-43 operates inseries with the relay A-4 Fig. 4 and lights the supervisory lamp 100 asa ringing signal to the toll operator. Relay (ir- 2, Fig. 2, cuts oil'the bridge including theright winding of relay C-2 and relay A-2. Theoperator now operates her ringing key R K which impressesalternatingcurrent upon the talking conductors which operates thealternating current relay C-4 which in attracting its armature operatesthe relay 471. This relay in attracting its left armature opens thecircuit heretofore traced, which has been holding relay F-5, Fig. 5,energized. This relay in retracting its. armature 537 connects ringingcurrent to the called .line through its upper winding. This ringing-current is automatically applied until the called party removes hisreceiver, resulting in an increase in the current through the upperwinding of relay F--5 causing the same to operate removing the ringingcurrent. The attraction of the armature 535 of this relay closes alocking circuit for the same over grounded control conductor 500. Theextension of the tip and ring conductors by relay F-5 to the called lineoperates relay 473 over which'talking current is fed to the called line.Relay 473 in operating energizes relay B-4 which in attracting its outerleft hand armature applies ground to the conductor 474, and outer rightarmature of relay F-4, conductor 418, contact 446, armature 447 of relay(ir- 4, conductor 448, brush 449, multiple 450, conductors 451, 500,front contact and armature 535 of relay F-5, lower winding of relay F-5to battery, to hold up rela F--5 independently of relay 471. Relay l34in opening its contacts 411, 401 opens the connection of battery throughthe windings of relay A-4 to the talking conductors 407, 408, leadingback to the operators position which causes the deenergization ofsupervisory relay B-43. This relay in retracting its armatureextinguishes the supervisory lamp 100 which notifies the operator thatthe subscriber has responded. Talking current is fed to the Called lineover the wind-ing of relay 473 and the repeating coil 404. This italking circuit is -a standard repeating coil transmission-circuit usedin long distance connections. Talkin current is fed to the calling linefrom te calling dista-nt exchange. During conversation the trunk leadingfrom the left hand windin s of rev peating coil 404 through the rig thand winding of the repeating coil (not shown) at the distant oiiice, isdry, in accordance with standard practice. y

Assuming now that the desired line when selected by the connector isbusy. In that event the test multiple 526, Fig. 5, is grounded. Whentest wiper 527 is set on the bus multiple 526, ground is extended overbrus 527, conductor 528, contact 544 of relay E-5, conductor 541armature 542 and back contact of relay Il-5, conductor 543, relay G-5 tofree ole of battery. 'Relay G-5 energizes and when E--5 releases as theimpulses terminate, locks itself up over the following circuit: freepole of battery, relay G5, conductor 543, armature 542 and back contactof relay H-5, conductor 541, make before break contact of relay E-e5,right armature and front contact of relay G-5, conductor 531, conductor515 to ground at the armature 516 and front contact of relay B5. RelayG-5 inthe case of a local call connects busy tone from the source 545 tothe calling line. this busy tone is not used, a flashing signal beinggiven to the operator instead. Relay G-5 in operating due to the linebeing busy revents test relay H-5 from operating w en E-5 releases. Whenbusy test relay G--5 operates a circuit is closed for rela D--5 fromfree pole of battery, upper winding vof D-5, conductor 578, conductor579, contact 5,80 of K--5, conductor 581, resistance 599, armature 582and back contact of relay E5, outer left armature and front contact ofG-5, inner right armature of relay J-5 and front Contact, conductor 531,515 to ground at armature 516 ,and front contactlo'f` B--5. Relay D--5reverses the direction of current flow I through the left winding ofrelay 461 (Fig. 4) which results in this relay operating. The leftarmature and front contact of relay 461 closes a circuit for operatingrelay F-4 as follows: battery, relay F-4, conductors. 469, 475, leftarmature and front contact of relay 461, conductor 476, .477, 470,armature 434 and front contact ofrelay G-4, conductor 415gto ground onthe right armature and front contact of relay 414. Relay F-4 reversesthe direction of current ilow in the circuit leading back to theoperators cord as in the case of an idle line to operate polarized relayF-2 which in turn operates relay G-2 to connect the talking conductorsof the cord through to the connector. The right armature ofnrelay461connects interrupter 479 to relay 471which in operatingintermittently applies ground to con-- ductor 400 in shunt of thecircuit leading over tip conductor 407 back to the operators cord. Thecircuit of relay 471 leads over the outer right front contact of relayD-4 to ground at the right armature of relay A-4. When the operatorrestores her dialing key, relay G-2 being operated, the intermittentground applied to conductor 400 by relay 471 shunts out the relay 1%.-43intermittently which causes the flashing of the lamp 100 at aV ratedifferent from that in the case where a selector found all the trunksbusy, for example, 120 flashes per minute. v

When the operator pulls out the plug TT from the trunk switching jackTSJ this causes the release of all switches and the return to normalcondition of all the apparatus including' the various locked up relays.

During the conversation the called subscriber by moving his hook downand up causes the supervisory lamp 100 at the toll operators position toflash as in manual ractice without releasing the switches.

his `is apparent from the preceding description inasmuch as relay 473 isin circuit with the called line so that it is energized while thehook'occupies its upper position and each time it attracts its armatureoperates the relay B-4 which removes battery and ground from the trunkconductors lead.- ing back tothe supervisory relay B-43 and puts abridge across the relay A-4 to hold 1t operated to prevent release aslong as the subscriber has his receiver off the hook. When the calledsubscriber replaces his receiver this lights the' lamp 100 at the tolloperators position, Fig. 1;

The operator may rering'the subscriber if she desires to recall him byactuating her ringing key RK which operates relay C-4 to operate relay471 which in attracting its left hand Iarmature again releases relay F-5which initiates the automatic ringing operation at the connector. Thecontrol of this relay F-5 was removed from the relay 471 by theattraction of the outer left armature of relay B-4 when the calledsubscriber responded and is restored to the relay 471 and consequentlyto the operator when the called subscriber replaces the receiver anddeenergizes relay B-4.

When the operator desires to break down the connection after the calledsubscriber has replaced his receiver, she removes the plug TT from thetoll switching jack TSJ. sThis releases relay A 4, Fig. 4 which causesthe restoration of all the switches. If, however, the operator pulls outthe plug while thecalled subscriber still has his receiver ofi theswitch hook, the switches are not released since relay A-4 whichcontrols the release is maintained energized over the .followingcircuit: battery, left hand winding of relay A4, conductor 400, armature480 and -front contact o f relay B-4, resistance 481, conductor 412,right hand winding of relayl A-4 to ground at the lower normalcontact ofcontacts 413, it being noted that the relay B4 which controls this loopcircuit is itself controlled by relay 473 in circuit With the calledline and controlled at the switch hook of said line.

Assuming, however, that the called subscriber has replaced his receiver,when the operator removes the plug, relay A-'4 in releasing deenergizesrelay 414. Relay 414 in retracting its outer left armature removesground from the sleeve conductor 482 leading over the sleeve conductorto the relay 336 which in releasing its'armature removes ground from thesleeve wire 325. The removal 'of this ground releases relay D-3whereupon the release magnet 340 operates as follows: free pole ofbattery, magnet 340, off normal switch contact 341, lower armatures andback contacts of relays B-3 and A3 to ground at the armature 311 andback contact of relay D-3. Thus the first selector is restored and uponreaching its normal position opens the off normal springs 313 and 341.The removal of ound from conductor 415, by the retraction of right handarmature of relay 414 releases relay (ir-4 and the retraction of theright hand armature of relay A-4 and inner left armature of relay 414closes a circuit for the release magnet 483 at the selector repeater.

gli

The slow relay 430'is energized in parallel v with the release magnetand opens the circuit to the test brush 438 during restoration at itsarmature 436. At its armature 484 it short circuits the right handwinding of relay A4. At its upper armature it closes a locking circuitfor itself which is opened when t-he off normal switch aumes its normalposition. The opening of the circuit of the tip and ring conductors 510.546 causes the release of relays A-5, B-5, J-5, Fig. 5, which results inthe closure of `.the following circuit for connector release magnet 540:free pole of battery, magnet 540, left hand contact of off normal switch520, back contact and lowermost armature 583 of relay D-5. lowerarmatures and back contacts of relay B-5 and A-y to ground. Theconnector uponreaching normal position restores the ofi normal switch520.

What is claimed is:

1. In a telephone exchange system, the combination with telephone lines,automatic switches, groups of trunks terminating therein, an operatorsposition, a. signal thereat, means controlled from said position forsetting said switches to interconnect said lines over said trunks, meanscontrolled solely lby the' busy condition of the selected line foroperating Said signal in one Inanner, means controlledby the idlecondition of the selector line for operating said signal in a secondmanner and means controlledl by thebusy condition of a selected trunkgroup for operating said signal in a third manner. 2. In a telephoneexchange system, the combination with telephone lines, automaticselector switches, groups of trunks terminating therein, an operatorsposition. a lamp thereat, an impulse sender which restores to normalafter each set of impulses for setting said switches to interconnectsaid lines over said trunks, means'controlled solely by the busycondition of the selected line for flashing said lamp in one manner andmeans controlled by the busy condition of a selected trunk group forflashing said signal in a different manner.

3. In a tele hone exchange system, the combination with an ofliceincluding automatic switches, subscribers lines terminating therein,another oflice, a toll operators position thereat including a cordcircuit having a supervisory lamp therein, an impulse sender whichrestores to normal after each set of impulses associated with saidposition and controlling said switches, means actuated in case one ofsaid switches fails to find an idle trunk for flashing said lamp in acertain manner, and means actuated only in case the connector finds theselected line busy for flashing said lamp in a different manner.

4. In a telephone exchange system, the combination with a.telephoneline. automatic switches, groups of trunks terminating therein,anv operators position, a lamp there-at, means at said position forcontrolling said switches to interconnect said lines over said trunks,means controlled by the idle condition of said line for lighting saidlamp as a ringing signal, means controlled by the operator for causingringing current to be applied to the selected line, means controlled bythe response of the called party for cutting off the ringing current,means controlled by the busy condition of a selected trunk group forflashing said Vlamp at a certain rate, and means controlled solely bythe busy condition of the called line for flashing said lamp at adifferent rate.

5. In a telephone exchange system, the combination with telephone lines,automatic switches, groups of trunks terminating therein, an operatorsposition, means at said position for controlling said switches tointerconnect said lines over said trunks, a supervisory lamp at saidposition, a supervisory relay controlling the same, a polarized relaybridged across one of said trunks, means controlled by the idlecondition of the selected line for operating said polarized relay forcausing the energization of said supervisory relay, means controlledsolely by the busy condition of said line for closing an interruptedcircuit through said supervisory relay to flash said lamp at a certainrate, and' means controlled by the busy condition of a selectedtrunkgroup for closing an interrupted circuit tov intermlttently energizesaid supervisory relay for flashing said lamp at a different rate.

6. In a telephone exchange system, telephone lincs, automatic switches,a trunk circuit, an operators position, a cord circuit thereat havingmeans for controlling said switches to buildup a condition over saidtrunk lines'to a selected line, a supervisory lamp in said cord, asupervisory relay, a polarized relay in one-of said trunks, meanscontrolled by the idle condition of the se lected line for operatingsaid polarized relay to close the circuit of said supervisory relay,means controlled lsolely by the busy condition of the selected line forpreventing the operation of said polarized relay and for closing aninterrupted circuit to said supervisory relay to flash said lamp at acertain rate, and means controlled by the busy condition of a selectedtrunk group for closing an interrupted circuit to said supervisory relayto flash said lamp at a different rate.

7. In a telephone system, the combination withtelephone lines, groups oftrunks including automatic switches, an operators position, means atsaid position for building up a connection to a called line over saidtrunks and switches, a supervisory lamp at said position. a key at saidposition, a supervisory relay therefor. a circuit for said supervisoryrelay controlled by contacts of said key, means including a relayenergized when the selected line is found busyto interrupt said circuitto flash said lamp at a given rate when said key is restored and a'relayactuated by the busy condition of a selected trunk group for closing aninterrupted circuit when said key is restored to flash said lamp at adifferent rate.

8. In a telephone system, telephone lines, automatic switches. trunkgroups, an operators position, a lamp thereat. a dial at said positionfor building up a, connection to a called line over said trunks andswitches, a dialing key, and means controlled bythe busy condition of aselected group for flashing said lamp at a certain rate upon therestoration of said dialing key, and means controlled solely by the busvcondition of the selected line for flashing said lamp ata different rateupon the restoration of the dialing key.

9. In a telephone system, the combination with telephone lines,automatic switches. groups of trunks. an operators position, asupervisory lamp thereat, a dial at said position for building up aconnection to a called line over said trunks and switches,

a dialing key -for connecting said dial to said circuit and fordisconnecting said supervisory relay therefrom, means controlled by thebusy conditionl of a selected group for flashing said lamp at a certainrate upon the restoration of said dialing key,.and means controlledsolely bythe billy condition of the selected line for flashing said lampat a different rate upon restoration of said dialing key.

10. In a telephone system, the combination with telephone lines,automatic switches and grou s of trunks, an operators position, a dialthereat for vbuilding up connection over said trunks and switches, adialing key for connecting said dial to said trunks, a su rvisory rel'athereat, a lamp controlled t ercby, said ialing key when actuateddisconnecting said supervisory relay, means controlled by the idleconditions of the selected line and the restoration of said key forlighting said lamp, meansl controlled by the busy condition of aselected group and the restoration of said key for dashing said lamp ata certain rate, and means controlled solely by the busy condition of theselected line andrestoration of said key for flashing said lamp at adifferent rate.

11. In a telephone system, telephone lines, automatic switches, groupsof trunks, lan operators osition, a supervisory lamp thereat, a dial, adialing key for connecting said dial to said circuit to build up aconnection to a called line over said trunks and switches and tosimultaneously open the circuit of said supervisory relay, a cir cuitprepared by the finding of a selected group busy and closed upon therestoration of said dialing key -for dashing said lamp at a certa-inrate, a second circuit prepared solely due to the busy condition of theselected line and closed by the restoration of the key for flashing saidlamp at a different rate, and means controlled by the idle condition ofthe selected line for preventing the closure of either of said circuits.

12. In a telephone system, the combination with telephone hnesterminating in different oflices, automatic switches, groups of trunks,an operators position, a supervisory relay and lamp thereat, a dial forcontrolling said switches to build up a connection from one oflice to acalled line in another oiiice over said trunks, means controlled by theidle condition of the called line for applying current to said trunk tooperate said supervisory relay to light said lamp, means controlled bythe response of the called party for removing battery from the trunk todeenergize said relay to extinguish said lamp, means controlled by thebusy condition of a selected trunk group to {iash said lamp in onemanner, and means controlled solely by the busy condition of trolled bythe idle condition of the called line for applying current to said trunkto operate Vsaid superviso relay to light said lamp, means controlle bythe response of the called partyv for removing battery from the trunktodeenergize said relay to extinguish said lamp, means controlled by thereplacing of the receiver by the called party for again applying currentto said trunk to operate said supervisory relay to light said lamp,means'V controlled by the busy condition of a selected trunkl group toflash said lamp at a given rate, and means controlled solely by the busycondition of a selected line for flashing said lamp at a different rate,i

14. In a telephone system, the combination with telephone lines, aconnecting circuit including automatic switches, an operators position,a sender thereat for controlling said switches to select the calledline,a supervisory lamp at said position, a polarized relay in saidconnecting circuit, means for reversing the `current in said connectingcircuit if the selected line is either idle or busy to operate saidpolarized relay to cause said lamp to light, and means actuated by thebusy condition of the called line for causing said lamp to flash.

15'. In a telephone system, the combination with telephone linesterminating in different oiices, an operators position at theoriginating oilice, a lamp at said position, a two-Wire trunk extendingfrom said position to an automatic oiice, automatic switches thereat, asender at said position for setting said switches to connect with thecalled line, a polarized relay in said trunk at the originating oilice,means for reversing the current flow in said trunk if the selected lineis idle or busy to operate said polarized relay to cause said lamp tolight, and means actuated by the busy condition of the called line forcausing said lamp to fiash.

16. Ina telephone system, the combination with telepllone linesterminating in different oiiices, an operators position at theoriginating office, a lamp at said position, a two-wire trunk extendingfrom said position to an automatic oflice, automatic switches thereat, asender at said position for setting said switches to connect with thecalled line, a polarized relay in said trunk at the originating oce, arelay at said automatic oirice for reversing the current How in v acircuit for said relay, two rela s severally controlling said reversingre ay circuit, means for operating one of said relays .to operate saidreversing relay when the called .l'ne is foundA idle, means foroperating said other relay to operate said reversln relay if the calledline is found busy, an additional means controlled by said other relayfor causing the subsequent flashing of said lam 17E.) In a telephonesystem, the combination with telephone lines terminating in differentoflices, an operators position at the originating oice, a lamp at saidposition, a two-wire trunk extending from said poisition to an automaticoice, -automatic switches thereat, afsender at said position for settingsaid switches to connect with the called line a'polarized relay in saidtrunk at the originating oilice, a relay at said automatic oilice forreversing the flow in said trunk to cause the lighting of said lamp, acircuit for said relay, two relays severally controllin said reversingrelay circuit, one of said re ays being polarized and included in thetrunk circuit to the connector, means actuated by the connector infinding the line idle for releasing one of said relays to operate saidreversing relay, means actuated by the connector finding the line busyfor reversing the current in said last named trunk to operate said lastmentioned polarized relay to cause the operation of said reversingrelay, and additional means controlled by said last mentioned polarizedrelay when operated for causing the flashing of said lamp.

18. In a telephone system, the combination with telephone linesterminating in different oiices, an operators position at theoriginating olice, a lamp' at said position, a circuit therefor, atwo-wire trunk extending from said position to an automatic office,automatic switches thereat, asender at said position for setting saidswitches to connect with the called line, a polarized relay in saidtrunk at the originating office, a relay at said automatic office forreversing the flow in said trunk to cause the closure of said lampcircuit, two relays severally controllin said reversing relay circuit,one of said re ays being polarized and included in the trunk circuit ofthe connector, means actuated by the connector in finding the line idlefor releasing one of said relays to operate saidV reversing relay, meansactuated by the connector finding the-line busy for reversing thecurrent in said last named trunk to operate said last-mentionedpolarized relay to ca use the operation of said reversing relay, and ashunt circuit intermittently closed about said supervisory relay by saidpolarized relay to causethe same to flash said lamp.

In witness whereof, I hereunto subscribe my name this 1st day ofDecember, A. D., 1920.

RAY STOKELY.

